1. Technical Field
The present invention relates to movable magnet type linear motors, and more particularly, to a movable magnet type linear motor with an improved end cover assembly.
2. Description of Related Art
FIGS. 1 and 2 illustrate a known movable magnet type linear motor, which comprises a stationary inner stator 1 that is structurally a hollow tube filled with a plurality of permanent magnets, a mover 2 that is constructed form a housing 3 accommodating therein a mover coil 4, wherein two end covers 6 are provided to seal two openings 5 at opposite ends of the housing 3 and each said end cover 6 is centrally formed with a hole 7 so that the stationary inner stator 1 is allowed to axially pass through and get slidably received in the mover 2. When a current flows through the mover coil 4, the mover coil 4 produces a magnetic field to interact with the permanent magnets inside the stationary inner stator 1 thereby driving the mover 2 to axially shift along the stationary inner stator 1. The known movable magnet type linear motor is advantageous because the stationary inner stator 1 and the mover 2 are associated with magnetic levitation means and no contact friction happens therebetween. As a result, component frictional loss is minimized and the movable magnet type linear motor performs swift running and stable braking.
However, the known movable magnet type linear motor has its defects.
That is, the end covers 6 of the mover 2 are typically fastened to the housing 3 by plural screws. In practice, since assembling each said end cover 6 requests at least 2 to 4 screws, it is labor-consuming in manual assembling operation and cost-consuming in automated assembling operation, both cases being uneconomical. Besides, operation of the known liner motor totally relies on the magnetic force of the permanent magnet and the mover coil 4, and thus the housing 3 and end covers 6 have to be made of non-magnetic material, which is mainly aluminum, for preventing magnetic interference. However, aluminum is relatively soft and tends to deform after repeated assembly and disassembly of the end covers 6 thereto. On the other hand, the cover ends 6 bear continuous axial impact caused by the magnetic force of the mover coil 4. Unfortunately, the direction where the screws are screwed to the housing 3 is parallel to this axial impact and the combination is challenged by the magnetic force of the mover coil 4. Consequently, the end covers 6 are likely to loose or come off after long-term use.